1. Field of the Invention
The present invention relates to a rubber composition for an automotive non-water liquid delivery hose, and an automotive non-water liquid delivery hose using the same. More particularly, the invention relates to a rubber composition used for an automotive non-water liquid delivery hose such as a vacuum brake hose, a fuel hose, an oil hose and the like, and an automotive non-water liquid delivery hose using the same.
2. Description of the Related Art
In general, a vacuum brake hose (also known as a master back hose) used for a vacuum servo unit for a brake connects a brake booster and an intake manifold (an engine) to each other, and has the function of transmitting a negative pressure generated in the intake manifold to the brake booster while absorbing vibrations of the engine and vibrations caused during driving. The vacuum brake hose is used for a circuit which transmits the negative pressure generated by the air intake of the engine to the brake booster to thereby increase a braking force and which also decreases an operating force of the brake. A fuel hose, on the other hand, connects parts of a fuel system to each other, and is required to have the function of safely transporting gasoline which is a fuel for automotive vehicles, light oil, or a fuel incorporating alcohol, methyl ester and the like without leakage and evaporation. An oil hose is required to transport oil and to have the function of appropriately transmitting a positive pressure exerted upon oil.
Since nonpolar hydrocarbon liquid and mist such as mineral oil and fuel pass through these hoses, acrylonitrile-butadiene rubber (NBR) which is an oil-resistant rubber is predominantly used as the material of an inner layer of such hoses, and chloroprene rubber (CR) having relatively good properties of ozone resistance and oil resistance is used as the material of an outer layer thereof. An example of the above-mentioned vacuum brake hose has been proposed which includes a tubular inner layer formed by using acrylonitrile-butadiene rubber (NBR), a reinforcing fiber layer formed on an outer peripheral surface of the tubular inner layer, and an outer layer formed by using chloroprene rubber (CR) on an outer peripheral surface of the reinforcing fiber layer, with an intermediate adhesive layer of chlorosulfonated polyethylene rubber (CSM) being provided between the inner layer and the reinforcing fiber layer, as disclosed in Japanese Patent Application Laid-Open No. 8-113769 (1996).
However, the hose disclosed in Japanese Patent Application Laid-Open No. 8-113769 (1996) is disadvantageous in the increase in costs because the intermediate adhesive layer of CSM, which is a relatively thick film, is present between the inner layer and the reinforcing fiber layer. The reduction in the thickness of the above-mentioned intermediate adhesive layer, however, results in insufficient interlayer adhesion between the inner layer and the outer layer. This makes it difficult to sufficiently meet requirements for higher performance and longer life of the hose product.
On the other hand, an example of an automotive water delivery hose proposed is an automotive hydraulic brake hose including an outer layer made of a blend of ethylene-propylene-diene and chloroprene rubber at a ratio of 10/0 to 3/7 by weight, as disclosed in Japanese Patent Application Laid-Open No. 6-24326 (1994).
However, the automotive hydraulic brake hose disclosed in Japanese Patent Application Laid-Open No. 6-24326 (1994) is not a non-water liquid delivery hose but a water delivery hose. It is therefore impossible to directly apply the hose structure disclosed in Japanese Patent Application Laid-Open No. 6-24326 (1994) to a non-water liquid delivery hose such as a vacuum brake hose and the like. Specifically, the outer layer of the automotive hydraulic brake hose disclosed in Japanese Patent Application Laid-Open No. 6-24326 (1994) is prepared by blending chloroprene rubber (CR) into ethylene-propylene-diene (EPDM) serving as a matrix. Thus, the direct application of the outer layer of the disclosed automotive hydraulic brake hose to a non-water liquid delivery hose such as a vacuum brake hose, a fuel hose and an oil hose presents a problem in significantly poor oil resistance.